The constantly increasing operational speeds of digital computers are creating a demand for corresponding increases in data storage capacities of magnetic tape recording and reproducing systems, while maintaining the special requirements of high speed digital tape systems.
Tape drives use separate read and write cores in order to verify that the data was written correctly to the tape. One method is to verify all written data, as the data is written, and re-write any defective blocks. This method is referred to as "read-after-write". Read-after-write is preferred because of high defect count on tapes and the open environment of tape drives.
Most tape drives operate in a bi-directional mode in order to avoid wasted rewind time. That is, data may be written while the tape travels in either the forward or reverse direction. It is desirable that tape recording and reproducing systems for use as computer data storage devices provide high data transfer rate and perform a read check on all written data. To achieve those goals, tape drives use parallel multiple read/write channels in order to achieve high data transfer rates. FIG. 1a offers a typical single channel head found in tape drives. One set of read and write cores is employed during the forward and reverse direction of tape travel. Thus only one track may be written at a time, in each direction. This head arrangement is inexpensive to manufacture, but not desirable for high data transfer rate recording. FIG. 1b shows a multi-channel head arrangement employing a plurality of read and write cores. This type of design may be applicable for high data transfer rate recording, but it is very expensive to fabricate. An alternative multi-channel head design uses three islands, as illustrated in FIGS. 2a and 2b, wherein the cores of the middle island are shared by the cores in the outer island. The disadvantages of such prior art multi-channel head designs are the price and cost. Head cost is the largest contributor to the cost of tape drives. Specifically, the large number of cores and island complexity coupled with low manufacturing yields and high labor content keep the head cost very high. On the other hand, single channel tape drives are less expensive to manufacture. However, such low end tape drives have been unable to keep pace with the ever increasing demand for high performance.
Thus, a hitherto unsolved need has remained for a low cost multi-channel recording head suitable for precise high data transfer rate recording.